1. Field of the Invention
The present invention relates to a plasma processing method, particularly, to a plasma processing method that can be applied to the etching process and the film-forming process included in the manufacturing process of a semiconductor device.
2. Description of the Related Art
Where a silicon oxide film such as a SiO2 film formed on a target substrate to be processed is removed by a plasma etching process with a photoresist film used as a mask, it was customary to use a gas of a fluorocarbon compound (CF series gas) such as octafluoro cyclopentene (c-C5F8) or hexafluoro-1,3-butadiene (1,3-C4F6), as disclosed in, for example, Japanese Patent Disclosure (Kokai) No. 2002-134479 and Japanese Patent Disclosure (Kokai) No. 2001-267294.
However, the etching with a high selectivity ratio relative to the photoresist is required in recent years in accordance with progress in the reduction of the thickness of the photoresist mask. To be more specific, it is of high importance nowadays to increase the etching selectivity ratio of the silicon oxide film relative to the photoresist film, i.e., the ratio of the etching rate of the silicon oxide film to the etching rate of the photoresist film. However, the etching gas of c-C5F8 described in the Japanese Patent Disclosure (Kokai) No. 2002-134479 and the etching gas of 1,3-C4F6 described in the Japanese Patent Disclosure (Kokai) No. 2001-267294 were not sufficiently satisfactory in terms of the etching selectivity ratio of the silicon oxide film relative to the photoresist film.
A serious problem is brought about in the case of using c-C5F8 or 1,3-C4F6 as the etching gas. Specifically, if the flow rate of the etching gas is increased in an attempt to increase the etching rate, a by-product is deposited within the etching hole so as to gradually lower the etching rate, with the result that the etching is stopped finally.
On the other hand, known is the technology of forming an amorphous CF film (α-CF film) having a low-dielectric constant on a silicon substrate or on an insulating film such as a SiO2 film by CVD (Chemical Vapor Deposition) using a CF series gas such as c-C5F8. However, in the case of using the conventional CF series gas, the deposition rate was not sufficiently high, leading to the demands for the technology that permits forming a film at a sufficiently high deposition rate.